In a radio communication system, when uplink radio communication from a radio terminal to a radio base station serving as a connection destination is performed, interference to neighboring radio base stations from the radio terminal is controlled (for example, refer to Patent Literature 1).
The same control is performed in LTE (Long Term Evolution) which is a 3GPP standard. In the LTE, information on an interference state called OI (Overload Indicator) is exchanged among radio base stations, so that one radio base station is considered to control interference (uplink interference from neighboring cells) from a radio terminal connected to neighboring radio base stations.
Specifically, one radio base station measures uplink interference power from the neighboring cells in units of radio resources called resource blocks (RBs), and transmits information of three values, which indicate “small interference”, “large interference”, and “very large interference”, according to the interference power, to the neighboring radio base stations. The neighboring radio base stations having received the information of three values can control transmission power (uplink transmission power) of connected radio terminals by using the information of three values. For example, when information indicating that the interference power is “very large” is received, the neighboring radio base stations control the radio terminals to reduce the uplink transmission power, thereby reducing uplink interference power in one radio base station.